28 



being propagated in undulations through the rocks or external 

 crusty would give rise to superficial oscillations, and thus cause 

 earthquakes. 



We shall note here a singular fact connected with the earth- 

 quakes of South America, viz. during nine years' observations 

 made by the writer; the oscillations were from east to west, 

 whilst the directions of their disturbances, and the rumbling 

 noise which generally accompanies them, were from south to north. 

 The former were generally confined to comparatively narrow 

 limits, whilst the latter extended often from Chili to central 

 America. 



This meridional action of the subterranean currents from 

 south to north is not confined to South America, but extends to 

 the northern hemisphere. And it appears from numerous ob- 

 servations made on the magnetic currents, that the power which 

 governs earthquakes and magnetic currents is the same. The 

 mean direction of the latter in South America corresponds to the 

 average direction of the subterranean disturbances. 



CHAPTER V. 



TERRESTRIAL MAGNETISM, OR THE EFFECTS OF THE POSI- 

 TIVE AND NEGATIVE POLES OF THE GLOBE ON ALL SUB- 

 STANCES WITHIN THE LIMITS OF THEIR ACTIONS. 



From a consideration of the general facts that have been stated 

 with respect to the effects of the galvanic current and its identity 

 with magnetism, it will be sufficiently evident that the earth acts 

 upon magnetized bodies in the same way as if it were itself a 

 magnetic battery; or rather, as if it contained within itself a 

 powerful magnet or battery lying in a position coinciding with 

 its axis of rotation. 



In order to make the above to agree with the facts as indi- 

 cated by the needle and other bodies possessing the property of 

 polarity, we must assume that the north pole of the earth is the 

 positive one, as the currents are moving towards it, therefore 

 the pole of decomposition, and the south the negative pole, i. e. 

 the pole of recomposition. Provided these poles be connected 



